Telephone system



June 10, 1930i E. E. .HINRICHSEN '1,752,985

TELEPHONE SYSTEM Original Filed March 50. 1927 2 Sheets-Sheet' 1 ,w GQ,

aff/Vex June l0, 1930. E. E. HlNRlcl-ISENA 1,762,986

' TELEPHONE SYSTEM original Fild March' so. 192'7v 2 sheets-sheet 2 Si mi. -k L i c *s 1%@ I w A s E a g1 Sw l. I

Patented June 10, 1930 P'ArENr oFFIc-Ej EDWARD E. y:1IrNnlc1acsnN'or New Your;I NQQY., nssIGNoR 'ro BELL TELEPHONE LABORATORIES; rNconPonATEn or vNnwjvoiarz, `Nif.; A CORPORATION orY NEW YORK TELEPHONE s YsrEM Application :nea Mareh3o1a27seria1n. 179,433, 'Rneweu December 1e, 19295 This invention'relates to telephone systems and more particularly to improvements -in trunking systems. E. f

Y In accordance with thisinif'ention thereis x5 provided a trunk circuit having a talking battery supply and a 'cord rcircuit which provides talking battery through a repeating coil when it is used for connecting ordinary subscribersilines, but when the cord circuit is Y V connected to the trunk, the repeating coil and vtalking battery iuV the cord are vrendered'in-y effective i j The trunk land cord are further arranged so that when thecord is used for'conn-ecting ordinary subscribersj lines, thesupervisory' signaling arrangement in the cord circuit is controlled by the lines in the Vusual manner, while when the ccrdisiconnected to the trunk, the supervisory control of the connection is 20 transferred to the'operatofs vcordfatthe distant 'end 'of the trunk, that is,'thesignals .in

`- the first mentioned cord are then y'controlled by the'distant operator who hasconnected to the distant end ofv thetrunk Vwith oneof her The intentionhasbeen illustrated in the accompanyingk drawings,l in which Y ig; 1 shows a cord circuit arranged in accordance with this invention and an ordinary 3o common battery subs-cribers line;

Fig; 2 shows a trunk circuit of the so-called recording and completing typ-e arranged kin accordance withV thisV invention; and;r also a portion of a standard recording and completing or toll operatoi"s'cord circuit. This figure scribers line. 1 I f i i The recording and completing trunk T shown in Fig. 2 isof the type whereby `toll i 'connections maybe made between an ordinary-subscribens line, such as 1, to a toll operators cord, such as C; through the A opera. tors cord at A, or connections from the toll operators cord C to aztoll switching opernates in a p lug 102. i To yclearlyY set forth 'the Various eaturesof the invention, a description will now be made of a call from' the subscribers line lto the subscribers vline 106, through'the cord circuit A,

also shows an ordinary 'common `battery vsub ators position' TSv where the trunk 'T termifollowed by a description of call from the subscriber-sfline. l'to the tolloperatorzatG a through the cord circuit A and trunk T', and v finally a description will bemade of a'call romthe toll operators cordC through the. trunk T to Van jordinary subscriberis line through the toll switching operatorsvposition TSL v l Y Y r`Whenthe subscriber of linel takes his re- Hceiver ofi' the hook, the signal 2 is actuated in'theusualmanner and the operator at cord Ak answers byuconnecting her plug 3 with `jack 4: of line l vand thereby causes the signal 2 tobe extinguished as is. well known vinthe art. `-A connection is nowcompleted from the'subscribei"s loop through repeating coil 5 toground and battery at the upper inner and*y lower inner armatures and back contacts4 of relay 6. To communicate with ythe calling subscriber7 the operator at Ak now, 'l0v 'Y actuates her talking key 7 to. connect her telephone setvnotfshown but-connected tothe g leads .marked 8, to the tip and ringcondu tors ofthecord A. y,

The ,operator at AV then receivesfrom the calling subscriber the number desired. f If' the wanted line, for example line 106, can be reachedthrough a multiple jack 103 at this operators position, the operator will simply e insert'plug 10 intoack 103. This connection operates through the sleeve circuit, the Inarginal vrelay `r,11 and relay 6 due'tothe low-'resistance Aof the winding of cut-off relay 104.

.How-ever, the operationfofrelayll opensfat its' make-beforeebreak contacts .the circuitv `for .85 relay 6 Ywhichf-releases `Vimmediately, while the circuit forl the marginal relayrll now eX-v tended through the upper inner armature and front contact through signal 13V to battery. This causes the signal 13to light for supervision. l The operator at Arnow callsthe subscriberof the line'106 byoperatin'g her usual ringing key 20, connected across'the tip and` ring'conductors of'cord A. VjVvVhen the subscriber of Vline 106 answers the` Gallia circuit is completed'through the A Vsubscribers loop tothe battery and ground through the windingof supervisory relay 15, the right yhand windingsof repeatingvcoil 5 and the upper outer armature and front 'conseA f tact and the lower armature and front `conis operated.

tact of relay 11. The supervisory relay 15 operates to extinguish lamp 13 to indicate to `the operator at A that the called subscriber has answered. A talking connection will now therefore be completed between the calling subscribers line 1 and the called subscribers line and conversation between the subscribers `may begin. It should be noted that this 'connection is of the usual common battery type with' the battery fed through the repeating coil 5.- The battery for the calling `subscribers line is, as hereinbefore stated, supplied through the armatures of relay 6, while the battery for the called subscriber is supplied directly through the right hand windings of repeating coil 5. Supervision in this case is identical with the usual supervision in cord circuits of this typeV and need not be further described. i

A connection from the subscribers line 1 to a wanted subscribers line through cord circuit A, trunk T and the toll opera-tors cord C will now be described. The subscriber of line 1 is connected with the operator at A in the manner above described and when the operator receives the information that a toll connection is desired, she will insert plug 10 into jack 110. A circuit is then completed through the sleeve circuit for the operation of relay 6 in the cord circuit and relay 111 in the trunk circuit. This circuit may be traced as follows: battery, winding 0f relay 6, make-before-break contacts and the winding of relay 11, sleeve terminals of plug 10 and jack 110, outer left hand armature and back contact of relay 112, both windings of relay 111 in series, to ground. f

Due to theV high resistance of the right hand winding of relay 111 the marginal relay 11 will not operate in this circuit. rThe operation of relay 6 closes an unencumbered circuit between the tip and ring terminals of plug 10 and jack 110 follows: The tip connection is made through the upper outer armature and front contact of relay 6 and the upper outer armature and back contact of relayll, while theringconnection is cornpleted-t-hrough the lower armature and back` contact of relay 11. lThe operation ofrelay 6 removes the battery andground connection from the calling subscribers line by the operation of its inner upper and lower armatures and the left hand winnings of repeating coil 5 will be bridged across the tip and ring conductors' as long as the talking key 7 This latter connection extends from the tip conductor to the upper left hand winding of repeating coil 5, lower contacts of talking key 7, lower inner armature and front contact of relay'6, lower left hand winding of repeating coil 5, through the Winding of supervisory relay 16 to the ring conductor. l

The above mentioned through connect-ionv now extends from the loop of the subscribers line 1 through the upper armature and the lower inner armature and back contacts of relay 113 and the armatures and back contacts of relay 114 to ground, through the upper left hand winding of repeating coil 115 for the tip conductor, and to battery through the lower left hand winding of repeating coil 115 and the winding of relay 116 for the ring conductor. Relay 116 operates in this Vcircuit and closes a circuit for relay 117 as follows: battery, Winding of relay 117, outer lefthand armature and back contact of rela-y 118,7armature and front contact of relay 116, armature and front contact of relay 111 to ground. Relay 117 in operating closes an obvious circuit for the operation of relay 119. The operation of this relay connects the alternating currentl source at its upper armature and lower inner armature and front contacts to the trunk conductors of trunk T, through the left hand armatures and back contacts of relays 120 and 121, through the condenser 122 and the left hand winding of relay 123. This impulse of ringing' current is momentary only, as the operation of relay 119 closes a Vcircuit for relay 118 as follows; battery, winding of relay 118, lower outer armature and front 'contact of relay 119, lower outer armature 9 and back contact of relay 113, armature and front contactof relay 111 to ground. The operation of relay 118 opens the circuit for the relay 117 but as this relay is slow to release the opening of the circuit for relay 119 will be delayed a short interval sufficient to permit the operation of relay 123. RelayY 118 in operating closes a vlocking circuit for itself through its inner' right hand armature and front contact to the ground at the armature and front Contact of-relay 111. The operation of relay 123 closes an obvious circuit for signal 125 and also provides a locking circuit for itself through its inner left hand armature and left hand winding to the ground at the right hand armature and back vcontact of relay 120.V Signal 125 in lighting indicates Vto the toll operator at C that a connection is oesired over this trunk.

The toll operator in answering this call inserts plug 130 into jack 131 and thus closes an obvious circuit for the operation of relay 120. Relay 120 in operating causes the release of relay 123 so that lamp 125 is now eX- tinguished. Relay 121 is operated over an obvious circuit by the operation of relay 120 but the battery and ground supplied at the armatures andfront contacts of this relay have no effect on the circuits at this time, duc to the operation of relay 120. The connection of plug 130 into jack 131 also closes a circuit loop through relay 133 to the tip and ring conductors through the upper armature and the lower inner armature and back contacts of relay 119, right hand windings of repeating coil 115, make-.beforeebreak v.contacts of relay 135, to battery through the'vright hand winding of relay 136 and to ground through the left hand armature and'back contact of relayv135 and left hand winding ofrelay 136. This circuit causes the operationof relays r136 and 133. The operation of'relay 133 closes an obvious circuit for the lighting of supervisory lamp 137,while the operationof relay Y136 closes a circuit for the operation of relay 139 as follows; battery, winding yof relay 139, armature and front'contact of relay 136 to ground. Relay 139 in operating closes a. locking circuit for itself through its inner 'left hand armaturel and front contact to the ground at the armature and front contact of relay 111. This relay also closes a circuit for the operation of relay 135VK as follows; battery, right hand winding'ofrelay 135, armature and back contact offrelay 140, outer left hand armature and front contact of relay 139, outer left hand armature and front contact of relay,

11S, armature and front contact of relay 1,16

f to the ground at the armature and front contact of -relayllly Relay 135 in 'operating opens the above mentioned circuit loop through relays 133 and 136. Relay 133 releases and causes lamp 137 to beextinguished y to indicate tothe toll operatorat C that 'the connection to the calling subscriber has been completed. through the trunk T. Relay 136,

however, is maintained operated through itsV right hand Winding by a circuit completed at the right hand armature and front contact of relay 135 to ground. 1

As avtalking connection is now completed through repeating coil`115 from cordA to cord C the toll operator. at cordy C mayoon nect her telephone set, not shown, across the tip and ring conductors of thecord and communicate with the operator at A' and receive the number of the wanted subscriber. When this number is received the toll operator completes the connection tothe wanted subscriber in the usual manner. The portion of the wanted subscriber is completed, has not been shown as it is well known in the art and forms no part of this invention.

When the toll operator and the operator' at Alremove their telephone sets from their respective cords, conversation between the calling and called subscribers may begin and it will be noted that the circuit through the cord A for talking is a simpleconnection for'the tip and ring conductors without any bridges or other connections attached thereto, and that the talking battery'is supplied from the trunk T.

l l/Vhen conversation between the two subscribers is ended, either the calling subscriber or the toll operator mayv vinitiate the release of the connection. If the callingsubscriber hangs up his receiver first, relay 116 will be released. The release of relay 116 causesthe release of relay 135 and relay 135 in Treleasing completes' the above mentioned connection to battery and ground through the lwindings of relay y136for the operation of relay 133 in the-cord This operation of 'relay 133 causes the lighting of lamp .V137 to indicate to the toll operatorV that the calling subscriber has disconnected; The'toll operator now removes plug 130 from jack 131, thus causing the release of relay 120. Relay '120 causes the release of relay 121 whilek the removal of plug 1.130 from jack 1-31 causes .the release of relay-136.V Relay 136 in releasing causesfthe operation of relay 142, over a circuit from battery, Awinding of relay 142, outer right.' hand armature and front contactl ofV relay 13.9, armature and-back Contact of relay 136to ground. f Relay 142 inoperatingpro* vides a locking circuit for itself throu'glrits inner right hand armature andv frontdcontact,

to the ground at the armature and front, con-Y tact of relay 111, and also short-circuits the right hand high resistance winding of relay 111. circuit for relay 113 is lalso closed by the operationofrelay 142 as follows; battery, winding of relay 113, outer right hand armature andfront contact of relay 142, armature and back contact of relay 143 to ground. -Relay 113 in operating' opensrthe holding circuit at its lower outer armature and back contact: for relays 139 and 118 which now release.v l

operator at cord A that the subscribers have disconnected. She will then rremove plug 10 from jack110' and plug 3 from jack 4. The removal ofplug 10 from jack 110 causes the release of relayi111 and this relayfin'turn will release relays 142 and 113. cord circuit C, whereby theconnection to the VIf the toll operator Yat @disconnects by removing her plug130 from jack 131 before the subscriber of 'line 1 rhangsup his receiver, the connection will be released ina lsomewhat Adifferent manner, that is, relay will be `released causing the release of relay121,

but as relay 121'isfslow to release, battery and ground at the armatures and front contacts of vthis relay will be momentarily connected to the tip and ring conductors of trunk T. This eration vof relay 142 as follows; battery, winding of relay 142, outer left hand armature and back vcontact of relay 145,"armature and front contact` of lrelay 143 `to ground. v Relay 142 in operating closes a locking circuit for itself as hereinbefore mentioned, to the ground at the armature and front contact of relay 111 and short-circuits the high resistance winding of relay 111. It also causes the operation ofrelay 113 when relay 143 ris released. The operation of relay 113 opens the circuit for relay 116. rllie release of relay 116 opens the circuit for relay 135 which causes the release of relay 136.V Relay 136 causes the release of relay 139 which in turn releases relay 118 as relay 113 is operated. The short-cirouiting of the high resistance Winding of relay 111 causes lamp 18 to be lighted as hereinbefore described and the operator at cord A then reinoves the plugs of this cord from acks 110 and 4, respectively, as hereinbefore mentioned to cause the circuits to be restored to normal condition.

If the toll operator at C shoulddesire to recall the operator at line 1, she will operate her ringing key 147, thus connecting ringing current to the tip and ring of the trunk T, causing the operation of relay 143 which is also an alternating current responsive relay. This relay in operating closes the above mentioned circuit for the operation of relay 142. Relay 142 locks up, as hereinbefore mentioned, and on the release of relay 143 relay 113 is operated. Relay 136, however, remains operated even though relay 135 releases, so that relays 139 and 118 are not re leased on the operation of relay 113 and release of relay 116. As relays 139 and 113 are operated, the ring conductor ofA trunk vT from the cord A is connected through the Vlower inner armature and front Contact of relay 113 to the inner right hand armature and front contact of relay 139 through an interrupter 149`to ground, and as the high resistance Winding of relay 111 is short-circuit ed by relay 142, relay 11 operates to connect the ground and battery through the right hand windings of repeating coil 5 to the tip and ring conductors. Hence the supervisory relay 15 is now alternately operated and released by the circuit completed from the ground at the interrupter 149 to battery at the lower right hand winding of the repeating coil 5, these operations of the supervisory relay 15 causing the alternate lighting and extinguishing of signal 13 to recall the operator at A. In answering this call signal from the operator at C, the operator at A removes plug 10 from jack 110 momentarily and thus causes the relays 11 and 111 to be released, relay 111 causing the release of relay 142 and relay 142 in releasing causing the release of relay 113. On the insertion of plug 10 into jack 110, relays 6 and 116 are Vagain operated causing the reoperation of relay 135. The operator at A may now therefore operate her talking key 7 to communicate with thev operator at cord C. As relays 139 and 118 are maintained operated, the insertion of plug 10 into jack 11() will not cause the operation of relays 117 and 119 at this time.

If the toll operator at C desires to make a connectioii'over trunk T to the toll switching operators position at TS using the trunk T las aswitching truuk, she Will insert plug 130 in jack 131 t0 initiate the call. The operations of relays 120 and 121 are of no importance at this time. A circuit is established for the operation of relays 136 and 133. Relay 133 causes the lighting of signal 137 while relay 136 causes the relay 139 to be operated and as relays 111 and 118 are not operated, relay 145 is operated on the opeartion of relay 139 over a circuit as follows; battery, winding of relay 145, inner left hand armature and back contact of relay 118, armature and back contact of relay 111, lower outer armature and back contact of relay 113, inner left hand armature and front contact of relay 139 to theground at the armature and front Contact of relay Relay 145 in operating closes an obvious circuit for the operation of relay 112, and this relay in operating disables the trunk for calls to the toll operator at C by opening the circuit for relay 111 at the outer left hand armature and back Contact and by closing a busy circuit for the sleeve' lead through a resistance to battery through the outer left hand armature and front contact. The operation of relay 145 closes a circuit for the lighting of the toll switching operators guard lamp 150 as follows; battery, lamp 150, upper armature and back Contact of relay 151, outer right hand armature and front contact of relay 145, upper outer armature and back Contact of relay 153 to ground or to ground at the upper inner armature and back contact of relay 154. rlhe lighting of this lamp indicates to the toll switching operator that a connection is desired.

Relay 145 also causes the operation of relay Y 151 over a circuit as follows; battery, armaing of relay 151. Relay 156 in operating removes the battery through the upper winding of relay 151 but the circuit for holding relay 151 operative now passes through the lower winding of this relay. The operation of relay 151,prevents the corresponding relay of any other trunk, in the group, from operating as the common battery normally supplied at the back contact and armature ofrelay 156 is described.

removed on the operationfof relay 156. In other words, only one relay, such' as 151, in the group of trunks at this position, can be operated at any one time. The operation-ofrelay 151 changes the circuit for the'toll switching operators lamp 150 at the upper armature and connects the lamp through this armature and the corresponding front contact to a coininoii iiiterrupter 157 connected tol ground. Lamp 150 will therefore now become alternately lighted and extinguished to indicate to the toll switching operator that her telephone set is connected to this particular Circuit.

The manner in which the toll switching operators telephone set, which is not shown butl may be connected at the point 158, is associated with this particular trunk will now be Cn-the operation vof relay 156 and 151 a circuit is closed for the operation ofrelay 160 as follows; battery, armature and frontcontact of relay y156, lower,outerarma ture and front contact of relay 151, winding of relay 160 to ground. Relay 160 in operat-k ing connects the tip and ring lead of the operators telephone set connected at point 158 to the tip and ring conductors of trunk T through its lower armatures and front contacts. The operation Vofrelay 160 also causesv the operation of relay 161 over a circuit kas follows; battery, winding of relay 161, upper outer armature and front contact of relay 160, to the above mentioned ground atjtlie' inner right hand armature and front contact of relay 1/15, and this relay 160 in operatiii'gcloseskk an obvious circuit for theoperation of relay 135. The operation of relay 135 opens the connection of the tip and ring conductors of trunk T through the cord C so that relay 133 now releases'and lamp 137 is extinguished to -i indicate that the toll switching operators telephone set has been connected to the line 1t is noted, however, that relay 1,36Iremains Y operated as hereinbefore described on the operation of relay 135.V The toll `operator at C may now connect her telephone yset to the cord and thus get in communicative connection with thetoll switching operator and pass the' number of the wanted subscriber to ksaid operator. l 4- I A.

After this `number ,is received, the toll switchingoperator may Yremove rher telephone set manually from 'the circuit before shey inserts plug 102 in the multiple jack of,y the wanted. subscribers line, not shown.V

However', the circuits are so reiiergized that in case she does not remove lier Atelephone set before she inserts the plug, theset will beV relay-,153,-inner upperarmature and front contact of relay 160,-key 163 to ground. Re-`V lished through its left hand winding by the operation of keyv 1,63. Relay 156 is maintained operated temporarily inorder 'to'prei ventany other trunk from beingA connected with thetoll switching operato-rs telephone set until this ykey has been released.V There'- lease of relay 151V opensthe flashing circuit for lamp 150 and reestablishes the original circuit for lighting this lamp steadily'. ltl

ysliouldrbe noted iii this connection lthat the's ground for this lampY circuit at theiarniature and back contact of relay 153 is .newl removed while the other ground hereinbefore mentioned at the armature and back Contact Y of relay 154 remains, so thatthis lamp circuit The release of relay 151 also opensthe circuit for-relay 160 which releases. Relay 161, however, vremains operated vas it established on its operation a locking circuit through tothe ground at the inner right hand armature and front contact of relay 14:5 independent of the original energizing circuit. v Therelfore', relay 135 is maintainedoperated while the toll switching operators'teleplioiiejset is disconnected on the release of relay 160. The

operation ofrelay 153 also connects the tip y and ring conductors from the plug L102 to the tip and ring conductors of the trunk T at the left hand side of the repeating coil 115.` Another relay operated by relay 153 is relay 113.'V Y

The circuity for this relay iso'bvious.. Relay 113 disconnects the tip and'lring conductors from the terminals of jack to prevent rconnections being made to the trunl. The operation Vof relay 113 also closes a circuit for the operation of vrelay 118, as follows;v battery,

, wiiiding'of relay'118, lower inner outerarmature and front-contact of'relay 113, inner -iio left hand armature and front" contact ofrelay y 139 to ground at the armature and front contact of relay 136. Relay 118 providesa lockcuit thro-ugh the lower outer armature.` and front-contact of relay 111,3,"throughvits inner right hand armature' and front contact to the above mentioned ground at the armature and front contact of relay 136.' l

The circuit is now'in condition for establishing aA connection to the wanted `subring circuitfor itself, independent of the cir- 'p scribers line and when the toll switching operator inserts plug 102 in the jack-of the wanted line, relay ,1541- isoperated through the sleeve lead in the usual manner. vThe op- 907. is now solely under control of relay 154.]V

. 95 f its upper inner armature and front contact lhereinafter be described.

eration of relay 154 removes the busy test connection from the tip of plug 102 by opening the connection through the lower outer armature and back contact ot' relay 154 and c-onnects the tip terminal of plug 102 to the tip conductor of trunk T at this armature and the corresponding front contact. The circuit for lamp 150 is opened through the operation ot' relay 154 so that this lamp will now be extinguished. The operation or" relay 154 causes the operation of relay 153 if it has not already been operated by the key 163. The circuit for this relay is in this case as follows; battery, winding of relay 153, upper outer armature and front Contact ot relay 161, lower inner armature and front contact of relay 154 to ground at the inner right hand armature and iront contact ot relay 145. Relay 153 locks as hereinbefore described and closes a circuit for holding relay 113 operated when relay 143 operates as will The circuit for relay 161 is opened at the make-betore-break contacts of relay 154 on the energization of this relay, and relay 161 in releasing opens the circuit tor relay 135. Relay 135 in releasing closes the above mentioned circuit for of relay 153, in case kev 163 has not beenoperated, relays 151 and 160 as well as relay 156 will release to disconnect the toll switching operators telephone at this time.

The toll operator at C will now actuate her ringing key 147 and transmit ringing current to the trunk T to cause the operation of relay 143 over a circuit as hereinbefore mentioned. Relay 143 inoperating closes a circuit for the operation of relays 114, 140 and 135. This circuit may be traced from battery, through the lett hand winding of rela-y 135, winding of relay 140, winding of relay 114, outer lett hand armature and front contact of relay 145 to ground at the armature and front contact of relay 143. All three relays will operate in thiscircuit. The operation of relay 140 performs no useful functionY at this time while the operation of relay 135 holds the relay 136 operated during the ringing period. The operation of relay 114 applies ringing current through its armatures and front contact over the tip and ring conductors to the wanted subscribers bell.

`When the subscriber answers the call by removing his receiver from the hook relay 116 will be operated through the subscriberis .loop over the circuit established through the armatures of relays 153 and 154. Relay 116 in operating closes a circuit as hereinbefore traced for maintaining of relay 135 operated when key 147 is released. Relay 133 is thereby maintained released to keep lamp 137 extinguished as an indication to the toll operator that the calling subscriber has answered the call. A connection is now completed from the called subscriber through to the toll switching operators positions and the toll operators position, the latter operator having previously established a connection to the calling subscribers line. Conversation between the calling subscriber and the called subscriber may now begin.

In breaking down this connection, should the called subscriber hang up his receiver iii-st, relays 116 and 135 would be released in succession and consequently lamp 137 lighted to indicate to the toll operator that the called subscriber has disconnected. The toll operator now removes her plug 130 from jack 131 and thus causes the release` of relay 136 which in turn causes the release of relays 139, 145, 153, 113 and 118. The'circuit for the toll switching operators lamp 150 will now be completed over a circuit as follows; battery, lamp 150, upper armature and back contact'oil relay 151, outer right hand armature and back contact oli relay 145, outer upper armature and 'lront contact of relay 154 to ground. The lighting of this lamp indicates to the toll switching operator that the toll operator has released the connection and the toll switching operator thereupon removes `plug 102 from the multiple jack of the called subscribers line so that relay 154 now releases to extinguish lamp 150 and release relay 112, which, it will be noted, was held operated through a locking circuit esta lished through its inner right hand armature and front contact to ground at the uil-per outer armature and front contact or" rel y 154. The purpose of maintaining re- 112 operated until this time is to maintain the busy condition on the jack 110 andmain tain relay 145 operated after relay 113 operated as hereinbeiiore described.

lt the, toll operator at C disconnects becore the called subscriber hangs up his recei ver, relay 120 is released and eventually relay 121, but a .momentary impulse from battery and ground at the armatures and front contacts of relay 121 will be transmitted over the trunk '1 to cause the operation of relay 143. rllhis relay operates as relay 135 is maintained operated at this time due to the fact that relay 116 is operated. Relay 143 in operating closes a circuit for the operation of relays 114 and 140 and for holding relay 135 operative. The operation of relay 140, however, opens the original energizing circuitfor relay 135 so that when relay 143 releases, relay 135 will release before it can be reenergized through the circuit later completed on the release of relay 140, relay 140 being slow to release. That is, the release of relay 135 causes the release of relay 136 and this relay iii turn 'releases relays 139, 145, 153, 113 and 118. Thus the original energizing circuit forv tem disclosed and described, but that many f modifications of the invention could'readily be made without departing from the 'spirit thereof.

l hat is claimed is: Y n 1. In a telephone exchange system, incom-r ing lines, outgoing lines, a link circuit connecting an incoming line with an outgoing line, a repeating coil associated with said link circuit, means for establishing a low resistanc-e non-inductive path around said repeating coil through said link circuit, and means associated with certain of said outgoing lines for actuating said last mentioned means to establish said pathresponsive totheestablishing of a connectionbetween the link circuit and one of said last mentioned outgoing lines. Y y Y 2. ln a telephone exchange system, iiicoiiiing lines, outgoing lines, a link circuit for connecting an incoming line with an out-going line, a repeating coil associated with said link circuit comprising a primary windingand a secondary winding, means 'for opening said primary winding, and means associatedjwith certain of said outgoing lines for actuating said first mentioned `means responsive tothe establishing of a connection between the link circuit and one of said last mentioned outgoing lines.` Y

3. In a telephone exchange system, incoming lines, outgoing lines, a manual link circuit for connecting an incoming line with an .outgoing line, a repeating coil associated with said link circuit comprising a primarywinding and a secondary winding,means for opening the primary winding and for establishing a low resistance non-inductive path.

around said repeating coil, and means .associated with certain of said outgoing lines for actuating said first mentioned means in response to the establishing of' a connection between said link circuit and one of said last mentioned outgoing lines.

4. in a telephone exchange lsystem, incoming lines, outgoing lines, a link circuit for cone nccting an incoming line with "an outgoing line, a repeating coil Yassociated with said link circuit comprising a primary winding,v

and a secondarywinding, a source of current normally associated with said windings, means fordisconnecting said source of current from said primary winding, and rmeans vassociated with 'certainoi said outgoing lines for actuating said first mentioned means ref sponsive to the establishing of a connection between said linkcircuit and one of said last mentioned outgoing lines. f

5. In a'telephone exchange system, in comingvlines, outgoing lines, a link circuit for connecting an incoming line with an outgoing line, a repeat-ing coil associated with said link circuit, a source of talking currentnormallyV connected withV said repeating coil in suoli manner as to be suppliedto an incoming line when said link circuit is connected'therewith, and means associated with certain of said outgoing lines for causing said talking current to be disconnected from said incoming line when saidV link circuit is connected with one of said last mentioned outgoing lines.

(6. ln a telephone exchange system, incoming lines, outgoing lines of dieientcharacters, a link circuit for connecting the incom-y ing liiiewith' the outgoing line, and having its talking conductors normally open, a source of talkin g current connected normally across the talking conductors, means for controlling the connection of said source of talking current to said link circuit, and means associated with 'said outgoing lines for controlling said first mentioned means to retain said source of talking current across the talking conductors of said link circuit and close connections through Vthe talking conductors in response to the consaid talking conduct-ors and close connections through said conductors inV response to the connection of an outgoing line of the other character .to said link circuit.

V7. In a telephone exchange system, incoming lines, outgoing lines, a link circuit for connecting an 'incoming line with an outgoing line, a repeatingA coil comprising primary y windings and secondary windings, asource of talking current associa-tedwith said primary windings and supervisory signals associatedr withsaid link circuit, means for establishing 'a low resistance .non-inductive path around said rrepeating coiland source of talking current through said' linkcircuit,umeans associated with certain of said outgoing lines for 1 ciated with said'last mentioned outgoing line for controlling said signals.

' 8. ln a telephone system, a link circuitlat one exchange, .a link circuit at anotherexchange, at'runk between said exchanges, a re.- peating coil comprising primary windings and secondary Windings,`a source of talking current associated ,y with said primary `Vwindings and supervisory signals associated with said first mentioned link circuit, means for establishing a low resistance non-inductive path around said repeatinfg coil and source of talking current in said rst mentioned link circuit responsive to the connection of said link circuit With said trunk circuit, means responsive to the connection and removal of said second mentioned link circuit from said trunk circuit for actuating said signals in one characteristic manner, a source of ringing current, and means responsive to the connection of said source of ringing current with the said second mentioned link circuit and the transmission of ringing current therefrom to said trunk circuit for controlling said signals in a characteristically different manner.

In Witness whereof, I hereunto subscribe my name this 24th day of March, A. D. 1927.

EDWARD E. HINRICHSEN. 

